Control handle with rotational cam mechanism for contraction/deflection of medical device

ABSTRACT

A medical device has a distal member with a configuration that can be changed by means of a control handle with a control assembly employing a rotational cam, a shaft, and a pulley, where the rotational cam is rotationally mounted on a portion of the control handle for rotation by a user. The rotational cam operates on the shaft to move it proximally or distally depending on the direction of rotation which in turn rotates the pulley to draw or release a puller wire to change the configuration of the distal member of the medical device. The shaft is oriented along a diameter of the control handle. The shaft has two ends which extends through two axial guide slots in the portion of the control handle to sit two opposing helical tracks formed on inner surface of the rotational cam. The guide slots are parallel with the longitudinal axis of the control handle and therefore maintain the shaft&#39;s diametrical orientation as the rotational cam is rotated to move the shaft proximally or distally. Actuation of the puller wire by means of the control assembly can result in a change of the distal member&#39;s configuration, including deflection, contraction and/or expansion.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of and claims priority to and the benefit of U.S. patent application Ser. No. 15/627,260 filed Jun. 19, 2017, now U.S. Pat. No. 10,252,031, which is a continuation of and claims priority to and the benefit of U.S. patent application Ser. No. 14/981,353 filed Dec. 28, 2015, now U.S. Pat. No. 9,682,214, which is a continuation of and claims priority to and the benefit of U.S. patent application Ser. No. 14/101,300 filed Dec. 9, 2013, issued as U.S. Pat. No. 9,220,868, which is a continuation of and claims priority to and the benefit of U.S. patent application Ser. No. 12/960,286 filed Dec. 3, 2010, issued as U.S. Pat. No. 8,617,087, the entire contents of all of which are incorporated herein by reference.

FIELD OF INVENTION

This invention relates to a catheter, in particular, a control handle having multiple control mechanisms for deflecting and contracting portions of a medical device

BACKGROUND

Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. Atrial fibrillation is a common sustained cardiac arrhythmia and a major cause of stroke. This condition is perpetuated by reentrant wavelets propagating in an abnormal atrial-tissue substrate. Various approaches have been developed to interrupt wavelets, including surgical or catheter-mediated atriotomy. Prior to treating the condition, one has to first determine the location of the wavelets. Various techniques have been proposed for making such a determination, including the use of catheters with a mapping assembly that is adapted to measure activity within a pulmonary vein, coronary sinus or other tubular structure about the inner circumference of the structure. One such mapping assembly has a tubular structure comprising a generally circular main region generally transverse and distal to the catheter body and having an outer circumference and a generally straight distal region distal to the main region. The tubular structure comprises a non-conductive cover over at least the main region of the mapping assembly. A support member having shape-memory is disposed within at least the main region of the mapping assembly. A plurality of electrode pairs, each comprising two ring electrodes, are carried by the generally circular main region of the mapping assembly.

In use, the electrode catheter is inserted into a guiding sheath which has been positioned a major vein or artery, e.g., femoral artery, and guided into a chamber of the heart. Within the chamber, the catheter is extended past a distal end of the guiding sheath to expose the mapping assembly. The catheter is maneuvered through movements that include deflection of a distal portion of the catheter so that the mapping assembly is positioned at the tubular region in the heart chamber. The ability to control the exact position and orientation of the catheter and also the configuration of the mapping assembly is critical and largely determines how useful the catheter is.

Steerable catheters are generally well-known. For example, U.S. Pat. No. Re 34,502 describes a catheter having a control handle comprising a housing having a piston chamber at its distal end. A piston is mounted in the piston chamber and is afforded lengthwise movement. The proximal end of the elongated catheter body is attached to the piston. A puller wire is attached to the housing and extends through the piston, through the catheter body, and into a tip section at the distal end of the catheter body. The distal end of the puller wire is anchored in the tip section of the catheter. In this arrangement, lengthwise movement of the piston relative to the housing results in deflection of the catheter tip section.

The design described in U.S. Pat. No. RE 34,502 is generally limited to a catheter having a single puller wire. If bi-directional deflection is desired, more than on puller wire becomes necessary. Moreover, if more control is desired, such as a contraction of the mapping assembly, an additional puller wire is needed. Space is limited within a control handle and operation of puller wire control mechanisms must not interfere with components that extend through the control handle, such as lead wires, cables, and irrigation tubing. Moreover, it is desirable that the control mechanisms be arranged such that the catheter can be operated single-handedly by the user. Accordingly, a desire exists for a control handle capable of moving three puller wires for at least two independent movements, such as bi-directional deflection of the catheter shaft and contraction of the mapping assembly, preferably through a single-handed manipulation of the user. A further desire exists for a deflection/contraction mechanism without excessive stress or kinking to the tensile component by which deflection/contraction is accomplished, whether it is a puller wire, a contraction wire, or another component.

SUMMARY OF THE INVENTION

The present invention is directed to a medical device which has a distal member with a configuration that can be changed by means of a control handle with a control assembly employing a rotational cam, a shaft, and a pulley, where the rotational cam is rotationally mounted on a portion of the control handle for rotation by a user. The rotational cam operates on the shaft to move it proximally or distally depending on the direction of rotation which in turn rotates the pulley to draw or release a puller wire to change the configuration of the distal member of the medical device. The shaft is oriented along a diameter of the control handle. The shaft has two ends which extends through two axial guide slots in the portion of the control handle to sit two opposing helical tracks formed on inner surface of the rotational cam. The guide slots are parallel with the longitudinal axis of the control handle and therefore maintain the shaft's diametrical orientation as the rotational cam is rotated to move the shaft proximally or distally. Actuation of the puller wire by means of the control assembly can result in a change of the distal member's configuration, including deflection, contraction and/or expansion.

In one embodiment, a catheter for use in a patient's heart, especially for mapping a tubular region of the heart, includes a catheter body and a deflectable intermediate section distal the catheter body. Distal the intermediate section is a mapping assembly that has a generally circular portion adapted to sit on or in a tubular region of the heart. A control handle of the catheter allows for single-handed manipulation of various control mechanisms that can deflect the intermediate section and contract the mapping assembly by means of a deflection control assembly and a rotational control assembly. The deflection control assembly has a deflection arm and a rocker member. The rotational control assembly has an outer rotational cam, a shaft and a pulley. A pair of puller members are responsive to the deflection control assembly to bi-directionally deflect the intermediate section. A third puller member is responsive to the rotational control assembly to contract the generally circular portion of the mapping assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. It is understood that selected structures and features have not been shown in certain drawings so as to provide better viewing of the remaining structures and features.

FIG. 1 is a top plan view of one embodiment of the catheter of the present invention.

FIG. 2A is a side cross-sectional view of an embodiment of a junction of a catheter body and an intermediate section, taken along a first diameter.

FIG. 2B is a side cross-sectional view of the embodiment of the junction of FIG. 2a , taken along a second diameter generally perpendicular to the first diameter.

FIG. 3 is a side view of a distal portion of the catheter of FIG. 1, including an intermediate section and a mapping assembly.

FIG. 4 is a longitudinal cross-sectional view of the intermediate section of FIG. 3, taken along line 4-4.

FIG. 5 is a schematic view of the mapping assembly showing one arrangement of the ring electrodes.

FIG. 6 is a longitudinal cross-sectional view of the mapping assembly of FIG. 3 along line 6-6.

FIG. 7 is a side cross-sectional view of an embodiment of a distal end of the mapping assembly of FIG. 3.

FIG. 8a is a side cross-sectional view of an embodiment of a junction between the intermediate section and the mapping assembly, taken along a first diameter.

FIG. 8b is a side cross-sectional view of an embodiment of a junction between the intermediate section and the mapping assembly, taken along a second diameter generally perpendicular to the first diameter.

FIG. 9 is a top plan view of an embodiment of a control handle housing half including an embodiment of a deflection control assembly.

FIG. 10 is a top perspective view of an embodiment of a rocker member of a deflection control assembly.

FIG. 11 is a bottom perspective view of an embodiment of a rocker member.

FIG. 12 is a side view of an embodiment of a pulley of a deflection control assembly.

FIGS. 13a-13c are schematics of an embodiment of the deflection control assembly in neutral and rotated configurations.

FIG. 14 is a longitudinal cross section of an embodiment of the deflection control assembly and tension control assembly mounted on a control handle.

FIG. 14a is a detailed view of a portion of FIG. 14, including an embodiment of a retaining nut and a tension screw.

FIG. 15 is a partial perspective view of an embodiment of a first control handle housing half.

FIG. 16 is a perspective view of an embodiment of a deflection arm.

FIG. 17 is a perspective view of an embodiment of a tension control dial.

FIG. 18 is a perspective view of an embodiment of a locking plate.

FIG. 19 is a partial perspective view of a portion of an embodiment of a control handle.

FIG. 20 is a partial perspective view of a portion of an embodiment of a deflection arm and a tension control member mounted on a control handle.

FIG. 21 is a partial perspective view of a portion of an embodiment of a second control handle housing half and a retaining nut, the second control housing half adapted to oppose the first control handle housing half.

FIG. 22 is a perspective view of the tension control dial of FIG. 17 and locking plate of FIG. 18 as assembled.

FIG. 23 is a perspective view of an embodiment of a rotational control assembly.

FIG. 24 is an exploded perspective view of the rotational control assembly of FIG. 23.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the present invention is directed to a catheter 10 with multiple control capabilities for mapping and/or ablation of the heart. In the illustrated embodiment of FIG. 1, a catheter 10 comprises an elongated catheter body 12, a deflectable intermediate section 14 at a distal end of the catheter body 12, a tip section 15 including a mapping assembly 17 at a distal end of the intermediate section 14, and a multi-functional control handle 16 at a proximal end of the catheter body 12 for controlling portions of the catheter, for example, deflecting the intermediate section 14 and contracting the mapping assembly 17.

With reference to FIGS. 2A and 2B, the catheter body 12 comprises a single, central or axial lumen 18. The catheter body 12 is flexible, i.e., bendable, but substantially non-compressible along its length. The catheter body 12 may be of any suitable construction and made of any suitable material. A suitable construction comprises an outer wall 22 made of a polyurethane or nylon. The outer wall 22 comprises an imbedded braided mesh of stainless steel or the like to increase torsional stiffness of the catheter body 12 so that, when the control handle 16 is rotated, the tip section of the catheter 10 will rotate in a corresponding manner.

The outer diameter of the catheter body 12 is not critical, but is preferably no more than about 8 French. Likewise the thickness of the outer wall 22 is not critical. The inner surface of the outer wall 22 is lined with a stiffening tube 20, which can be made of any suitable material, e.g., polyimide. The stiffening tube 20 is held in place relative to the outer wall 22 at the proximal end of the catheter body 12. A first glue joint 23 is made between the distal ends of the stiffening tube 20 and the outer wall 22 by a fast drying glue, e.g. Super Glue®. Thereafter a second glue joint 25 is formed between the proximal ends of the stiffening tube 20 and outer wall 22 using a slower drying but stronger glue, e.g., polyurethane.

The stiffening tube, along with the braided outer wall 22, provides improved torsional stability while at the same time minimizing the wall thickness of the catheter, thus maximizing the diameter of the single lumen. The outer diameter of the stiffening tube 20 is about the same as or slightly smaller than the inner diameter of the outer wall 22. Polyimide tubing is suitable because it may be very thin walled while still providing very good stiffness. This maximizes the diameter of the central lumen 18 without sacrificing strength and stiffness. Polyimide material is typically not used for stiffening tubes because of its tendency to kink when bent. However, it has been found that, in combination with an outer wall 22 of polyurethane, nylon or other similar material, particularly having a stainless steel braided mesh, the tendency for the polyimide stiffening tube 20 to kink when bent is essentially eliminated with respect to the applications for which the catheter is used.

In one embodiment, the outer wall 22 has an outer diameter of about 0.092 inch and an inner diameter of about 0.063 inch and the polyimide stiffening tube 20 has an outer diameter of about 0.0615 inch and an inner diameter of about 0.052 inch.

As shown in FIGS. 2A, 2B and 4, the intermediate section 14 comprises a shorter section of tubing 19 with multiple off-axis lumens, for example, first, second, third and fourth lumens 30, 31, 32 and 33. The tubing 19 is made of a suitable non-toxic material which is preferably more flexible than the catheter body 12. A suitable material for the tubing 19 is braided polyurethane, i.e., polyurethane with an embedded mesh of braided stainless steel or the like. The outer diameter of the intermediate section 14, like that of the catheter body 12, is preferably no greater than about 8 French. The size of the lumens is not critical. In one embodiment, the intermediate section has an outer diameter of about 7 French (0.092 inch) and the lumens are generally about the same size, having a diameter of about 0.022 inch, or selected lumens can have a slightly larger diameter of about 0.036 inch.

A means for attaching the catheter body 12 to the intermediate section 14 is illustrated in FIGS. 2A and 2B. The proximal end of the intermediate section 14 comprises an inner counter bore 24 that receives the outer surface of the polyimide stiffener 20. The intermediate section 14 and catheter body 12 are attached by glue 29 or the like.

As shown in FIGS. 2A and 2B, extending through the single lumen 18 of the catheter body 12 are various components, for example, lead wires and multiple puller members, and any other wires or cables. Longitudinal movement of the puller members relative to the catheter body 12 enable user control of various parts of the catheter via the control handle. In one embodiment, the puller members include a pair of deflection puller members 42 for deflecting the intermediate section 14 and a contraction puller member 35 for adjusting the mapping assembly 17 of the tip section 15.

A single lumen catheter body 12 can be preferred over a multi-lumen body because the single lumen 18 body can permit better tip control when rotating the catheter 10. The single lumen 18 permits the components passing therethrough to float freely within the catheter body. If such components were restricted within multiple lumens, they can build up energy when the handle 16 is rotated, resulting in the catheter body 12 having a tendency to rotate back if, for example, the handle is released, or if bent around a curve, to flip over, either for which are undesirable performance characteristics.

A deflection puller member 42 extends through the central lumen 18 of the catheter body 12 and into the second lumen 31 of the intermediate section 14. Another deflection puller member 42 extends through the central lumen 18 and into the fourth lumen 33 of the intermediate section 14. The distal ends of the deflection puller members 42 are anchored to the wall of the tubing 19 near the distal end of the intermediate section 14 by means of T-anchors 83 (FIG. 8B). In the intermediate section 14, each deflection puller members 42 extends through a plastic, e.g., Teflon®, sheath 81, which prevents the deflection puller members 42 from cutting into the wall of the tubing 19 of the intermediate section 14 when the intermediate section 14 is deflected.

As shown in FIG. 2B, compression coils 44 in surrounding relation to the deflection puller members 42 extend from the proximal end of the catheter body 12 to the proximal end of the intermediate section 14. The compression coils 44 are made of any suitable metal, e.g., stainless steel. The compression coils 44 are tightly wound on itself to provide flexibility, i.e., bending, but to resist compression. The inner diameter of the compression coils 44 is preferably slightly larger than the diameter of the puller wires 42. For example, when a puller member 42 has a diameter of about 0.007 inches, the compression coil 44 preferably has an inner diameter of about 0.008 inches. The Teflon® coating on the puller member 42 allows them to slide freely within the compression coils 44. The outer surface of the compression coils 44 is covered by a flexible, non-conductive sheath 27 to prevent contact between the compression coils 44 and other components, such as lead wires and cables, etc. A non-conductive sheath can be made of polyimide tubing.

The compression coils 44 are anchored at their proximal ends to the proximal end of the stiffening tube 20 in the catheter body 12 by glue joint 50 (FIG. 2B) and at its distal end near the proximal end of the intermediate section 14 in the second lumen 31 and fourth lumen 33 by glue joints 49 (FIG. 2B).

With reference to FIG. 3, at the distal end of the intermediate shaft 14 is the mapping assembly 17. The mapping assembly 17 comprises a generally straight proximal region 38 and a generally circular main region 39. The proximal region 38 is mounted on the intermediate section 14, as described in more detail below, so that it is generally a linear extension of the intermediate section 14. In one embodiment, the proximal region 38 has an exposed length, e.g., not contained within the intermediate section 14, ranging from about 3 mm to about 12 mm, more preferably about 3 mm to about 8 mm, still more preferably about 5 mm, but can vary as desired.

The generally circular main region 39 is generally traverse, if not also perpendicular, to the catheter body 12. The generally circular main region 39 can form a flat circle or can be very slightly helical. In one embodiment, the main region 39 has an outer diameter ranging from about 10 mm to about 25 mm, more preferably about 12 mm to about 20 mm. The generally circular main region 39 can curve in a clockwise direction or a counterclockwise direction. As shown in FIGS. 5, 6 and 7, the mapping assembly 17 is formed of a non-conductive cover or tubing 52 which can have any cross-sectional shape as desired. The non-conductive cover 52 can be made of any suitable material, and is preferably made of a biocompatible plastic such as polyurethane or PEBAX. The non-conductive cover 52 can be pre-formed into the desired generally circular shape of the generally circular main region 39. Alternatively, the shape of the generally circular main region 39 can be defined by a wire or other component extending through the non-conductive cover 52.

In the depicted embodiment, a pre-formed support member 54 extends through the non-conductive cover 52 to define the shape of the generally circular main region 39. The support member 54 is made of a material having shape-memory, i.e., that can be straightened or bent out of its original shape upon exertion of a force and is capable of substantially returning to its original shape upon removal of the force. On suitable material for the support member 54 is a nickel/titanium alloy. Such alloys typically comprise about 55% nickel and 45% titanium, but may comprise from about 54% to about 57% nickel with the balance being titanium. A suitable nickel/titanium alloy is Nitinol, which has excellent shape memory, together with ductility, strength, corrosion resistance, electrical resistivity and temperature stability.

A series of ring electrodes 26 are mounted on the non-conductive cover 52 of the generally circular main region 39 of the mapping assembly 17, as shown in FIG. 5. The ring electrodes 26 can be made of any suitable solid conductive material, such as platinum or gold, or a combination of platinum and iridium, and mounted onto the non-conductive cover 52 with glue or the like. Alternatively, the ring electrodes 26 can be formed by coating the non-conductive cover 52 with an electrically conducting material, like platinum, gold and/or iridium. The coating can be applied using sputtering, ion beam deposition or an equivalent technique. A suitable mapping assembly is described in U.S. Pat. No. 7,274,957, the entire disclosure of which is hereby incorporated by reference. If desired, additional electrodes (not shown) could be mounted along the intermediate section 14 and/or the generally straight proximal section 38.

The contraction puller member 35, for example, a contraction puller wire, is provided to contract the generally circular main region 39 to thereby change or reduce its diameter, for example, when mapping or ablating circular or tubular regions of the heart. The contraction wire 35 has a proximal end anchored in the control handle 16, which is used to manipulate the contraction wire as described further below. The contraction wire 35 extends through the central lumen 18 of the catheter body 12, through the third lumen 32 of the intermediate section 14 and into the non-conductive cover 52 of the mapping assembly 17. The portion of the contraction wire 35 extending through the non-conductive cover 52 is positioned on the side of the generally circular main region 39 closer to the center of the generally circular main region, as best shown in FIG. 6. The center of the generally circular main region refers to the center of the circle formed by the generally circular main region. With this arrangement, contraction of the generally circular main region 39 is dramatically improved over arrangements where the position of the contraction wire 35 is not so controlled.

As shown in FIGS. 5 and 6, within the mapping assembly 17, the contraction wire 35 extends through a plastic tube 55. In one embodiment, the plastic tube 55 comprise three layers, including an inner layer of polyimide over which a braided layer is formed, the braided layer comprising a braided stainless steel mesh or the like, as is generally known in the art. The braided layer enhances the strength of the plastic tube 55, reducing the tendency for contraction wire 35 to straighten the preformed curve of the mapping assembly 17. A thin plastic layer of polytetrafluoroethylene is provided over the braided layer to protect the braided layer from getting tangled with the lead wires 40 within the non-conductive cover 52. The plastic tube 55 has a proximal end anchored to the distal end of the intermediate section 14 in the third lumen 32 by glue or the like (FIG. 8a ). The support member 54 extends through the plastic tube 55 with the contraction wire 35 (FIG. 8a ). The distal ends of the support member 54 and the contraction wire 35 are soldered or otherwise attached to a small stainless steel tube 53 (FIG. 7). With this arrangement, the relative positions of the contraction wire 35 and the support member 54 can be controlled so that the contraction wire can be positioned on the side of the generally circular region 39 closer to the center of the generally circular region 39, as described above. The contraction wire 35 on the inside of the curve pulls the support member 54 to the inside of the curve, enhancing contraction of the generally circular region 39. Further, when the plastic tube 55 includes a braided layer, it keeps the contraction wire 35 from tearing through the non-conductive cover 52.

A third compression coil 46 is situated within the catheter body 12 and intermediate section shaft 14 in surrounding relation to the contraction wire 35 (FIG. 2A). The third compression coil 46 extends from the proximal end of the catheter body 12 to near the distal end of the third lumen 32 of the intermediate section 14. The third compression coil 46 is made of any suitable metal, e.g., stainless steel, and is tightly wound on itself to provide flexibility, i.e., bending, but to resist compression. The inner diameter of the third compression coil 46 is preferably slightly larger than the diameter of the contraction wire 35. The outer surface of the compression coil 46 is covered by a flexible, non-conductive sheath 68, e.g., made of polyimide tubing. The third compression coil 46 can be formed of a wire having a square or rectangular cross-sectional area, which makes it less compressible than a compression coil formed from a wire having a circular cross-sectional area. As a result, the third compression coil 46 keeps the catheter body 12, and particularly the intermediate section 14, from deflecting when the contraction wire 35 is manipulated to contract the mapping assembly 17 as it absorbs more of the compression.

The third compression coil 46 is anchored at its proximal end to the outer wall 20 of the catheter body 12 by the proximal glue joint 50 and to the intermediate section 14 by distal glue joint 72.

It is understood that glue joints throughout the catheter 10 may comprise polyurethane glue or the like. The glue may be applied by means of a syringe or the like through a hole made in the tubing walls. Such a hole may be formed, for example, by a needle or the like that punctures the tubing walls where the needle is heated sufficiently to form a permanent hole. The glue is then introduced through the hole to wick around the component(s) within the tubing to form a glue joint about the entire circumference of the component(s).

In the depicted embodiment of FIG. 7, the distal end of the mapping assembly 17 is sealed closed with a dome 51 of polyurethane glue or the like. A short ring 56, made of metal or plastic, and e.g., polyamide, is mounted within the distal end of the non-conductive cover 52. The short ring 56 prevents the distal end of the non-conductive cover 52 from collapsing, there by maintaining the diameter of the non-conductive cover at its distal end.

At the junction of the intermediate section 14 and the mapping assembly 17 as shown in FIGS. 8a and 8b , the non-conductive cover 52 is attached to the intermediate section 14 by glue or the like. The plastic tube 55 has its proximal end inserted and glued in the distal end of the intermediate section 14. The glue (not shown) from the plastic tube 55 can further serve to anchor the distal end of the third compression coil 46 in place within the third lumen 32. The support member 54 extends from the third lumen 32 into the plastic tube 55 within the non-conductive cover 52. The proximal end of the support member 54 terminates a short distance proximally from the distal end of the third lumen 32, approximately about 5 mm, so as not to adversely affect the ability of the intermediate section 14 to deflect. However, if desired, the proximal end of the support member 54 can extend proximally further into the intermediate section 14 and/or the catheter body 12.

The lead wires 40 attached to the ring electrodes 26 extend through the first lumen 30 of the intermediate section 14 (FIG. 2A), through the central lumen 18 of the catheter body 12, through the control handle 16, and terminate at their proximal end in a connector (not shown) which is connected to an appropriate monitor or other device for receiving and displaying the information received from the ring electrodes 26. The portion of the lead wires 40 extending through the central lumen 18 of the catheter body 12, control handle 16 and proximal end of the intermediate section 14 is enclosed within a protective sheath 62, which can be made of any suitable material, such as polyimide. The protective sheath 62 is anchored at its distal end to the proximal end of the intermediate section 14 by gluing it in the lead wire lumen 30 with polyurethane glue or the like to form glue joint 73.

The lead wires 40 are attached to the ring electrode 26 by any conventional technique. In one embodiment, each ring electrode 26 is mounted by first forming a hole in the non-conductive cover 52. An electrode lead wire 40 is fed through the hole, and the ring electrode 26 is welded in place over the lead wire and non-conductive cover 52.

With reference to FIG. 1, the control handle 16 comprises a generally elongated handle housing, which can be made of any suitable rigid material, such as plastic configured through a suitable molding process. In the illustrated embodiment, the housing includes two opposing halves 16 a and 16 b that generally mirror each other and are joined by glue, sonic welding or other suitable means along a longitudinal peripheral seam 28 around the housing. In the illustrated embodiment, the cross section of the handle 16 formed by the opposing halves changes along the length of the handle. A more distal portion 112 has a smaller, generally rectangular cross section. A mid-portion 114 has a larger, generally rectangular cross section. A more proximal portion 116 has a generally circular cross section.

In the illustrated embodiment of FIGS. 1 and 9, the control handle 16 houses components of a deflection control assembly 74 in the mid-portion 114. The deflection control assembly includes a deflection member or arm 75 that can be directly manipulated by an operator to control deflection of the intermediate section 14. The deflection arm 75 is rotatable about an axis 76 that is generally transverse or perpendicular to the longitudinal axis of the control handle. The deflection control assembly 74 has a rotatable rocker member 78 that acts on the deflection puller members 42 to deflect the intermediate section 14.

The rocker member 78 has a length L dimension, a width W dimension and a thickness T dimension (FIGS. 10 and 11). Along its thickness dimension T, the rocker member 78 is configured with two opposing annular formations 140 a and 140 b that define a central hole or passage 143 that extends through its entire thickness. The central hole 143 is aligned with the rotational axis 76 of the deflection arm 75. Along its length dimension L, the rocker member 78 also has two smaller holes 146 that oppose each other across the central hole 143. In each hole sits a pulley 147, for example, a snap bearing (FIG. 12), that has a rotational axis parallel to the axis 76. Each deflection puller member 42 enters the rocker member through slots 148 and a portion is wound around a respective pulley 147.

As understood by one of ordinary skill in the art, the rocker member 78 and the pulleys 147 are arranged such that rotation of the rocker member in one direction about the axis 76 draws back one puller member 42 to deflect the intermediate section 14 in that direction. With reference to FIGS. 13a-13c , as the rocker member 78 is rotated by means of the deflection arm (as represented by line 75), the pulleys 147 are displaced from a neutral position (FIG. 13a ) with one pulley 147 drawing a puller member 42 on one side of the catheter body 12 against its anchored proximal end for deflecting the intermediate section 14 toward that side (FIGS. 13b and 13c ).

Each deflection puller member 42 may comprise multiple segments. As illustrated in FIG. 9, each deflection puller member has a distal puller wire 42 a and a proximal fiber 42 b that are joined or connected at a location within the control handle 16 distal the rocker member 78. The puller wire 42 a and the tensile fiber 42 b of each deflection puller member are connected or secured to each other by a connector 154, e.g., a crimped brass ferrule covered by shrink tubing. Each puller wire 42 a extends through the catheter body 12 and the intermediate section 14. Each tensile fiber 42 b extends inside the control handle 16. In this manner, it is the more flexible tensile fibers 42 b that interact with the pulleys 147 and undergo repeated bending and straightening during deflection operations, as they are less prone to bending stress and fatigue failure.

Each puller wire 42 a is made of any suitable metal, such as stainless steel or Nitinol. Preferably each puller wire has a low friction coating, such as a coating of Teflon® or the like. Each puller wire has a diameter preferably ranging from about 0.006 inch to about 0.012 inch. Preferably both of the puller wires have the same diameter. Flat puller wires may be used in place of round puller wires. Their cross sectional dimensions should be such that they provide comparable tensile strengths as round puller wires.

Each tensile fiber 42 b may be of a high modulus fiber material, preferably having an ultimate tensile strength substantially in the range of 412-463 ksi (2480-3200 Mpa) such as High Molecular Density Polyethylene (e.g., Spectra™ or Dyneema™), a spun para-aramid fiber polymer (e.g., Kevlar™) or a melt spun liquid crystal polymer fiber rope (e.g., Vectran™), or a high strength ceramic fiber (e.g., Nextel™). The term fiber is used herein interchangeably with the term fibers in that the tensile fiber may be of a woven or braided construction. In any case, these materials tend to be flexible, providing suitable durability when used in wrapped engagement with the pulleys and the like for greater throw in deflecting the catheter tip. Further, they are substantially non-stretching, which increases the responsiveness to the manipulation of the control handle, and nonmagnetic so that they generally appear transparent to an MRI. The low density of the material causes it to be generally transparent to an x-ray machine. The materials can also be nonconductive to avoid shorting. Vectran™, for example, has high strength, high abrasion resistance, is an electrical insulator, nonmagnetic, is polymeric, and has low elongation under sustained loading conditions.

In the illustrated embodiment of FIG. 9, each tensile fiber 42 b extends proximally from the connector 154 toward the rocker member 78 where each is wound around a respective pulley 147 and turns about 180 degrees to double back toward the distal end of the control handle. Each proximal end of the tensile fiber 42 b is anchored by an anchor assembly 90 that includes a pair of racks 92, a slug 94 and a stop 96. The proximal end of each tensile fiber 42 b extends between a channel 91 defined by the pair of racks 92, and the proximal end of each tensile fiber is encased within a molded member or slug 94 sized to fit in and translate in the channel 91. Proximal the slug are the stops 96 that are adjustably positioned in a selected location along the racks 92, for example, by means of interlocking teeth 98 formed in the racks and the stops to releasably lock in the selected position against movement. The stops 96 are formed so that each respective tensile fiber 42 b can slide through or below them while blocking the slugs 94 from moving proximally past them. Accordingly, the stops 96 limit the proximal movement of the slugs 94 and anchor the proximal ends of the tensile fibers 42 b to effectuate deflection when each is drawn proximally by the deflection control assembly 74. During assembly of the control handle 16, before the two housing halves 16 a, 16 b are joined, the stops 96 are selectively positioned between the racks 92 to achieve a desirable tension in each tensile member. The interlocking teeth 98 of the racks 92 and stops 96 allow for fine adjustments in setting the tension.

The construction and assembly of the deflection control assembly 74 including the deflection arm 75 and a tension adjustment member 101 on the control handle 16 are described as follows. With reference to FIGS. 14 and 14 a, the rocker member 78 of the assembly 74 is situated between the two halves 16 a and 16 b of the control handle 16, with each of its annular formations 140 a and 140 b extending respectively through an opening 120 a, 120 b formed in the distal portion 114 of each housing half 16 a and 16 b.

The annular formation 140 a has recesses 160 (FIG. 10) exposed through the opening 120 a (FIG. 15) that receive protrusions 152 projecting from a facing surface 154 of the deflection arm 75 (FIG. 16) to rotationally couple the deflection arm 75 and the rocker member 78. The protrusions 152 can snap fit into the recesses 160 and/or be secured by adhesives, glue, sonic welding and the like. A central circular protrusion 156 from the deflection arm 75 fits into the hole 143 circumscribed by the annular formation 140 a of the rocker member 78. A suitable deflection assembly and control handle are described in co-pending U.S. application Ser. No. 12/346,834, filed Dec. 30, 2008, entitled DEFLECTABLE SHEATH INTRODUCER, the entire disclosure of which is hereby incorporated by reference. Another suitable deflection assembly with deflection sensitivity is described in co-pending U.S. application Ser. No. 12/211,728, filed Sep. 16, 2008, entitled CATHETER WITH ADJUSTABLE DEFLECTION SENSITIVITY, the entire disclosure of which is hereby incorporated by reference. Therein, a cam that is responsive to a deflection sensitivity knob can vary the separation distance between the two pulleys 147, thereby changing the deflection sensitivity of the deflection arm.

Opposing the deflection arm 75 is the deflection tension adjustment member or dial 101 (FIGS. 17 and 20) which is coupled to and indirectly engaged with the rocker member 78 by various mechanisms and parts and allows an operator to adjust the ease with which the deflection arm 75 can be rotated. Mounted primarily on the housing half 16 b, the illustrated embodiment of a tension adjustment assembly 100 includes the adjustment dial 101 (FIG. 17), a locking plate 102 (FIG. 18), a tension cap screw 103, a retaining nut 136 and a washer 119 (see FIGS. 14 and 14 a). A user rotates the dial 101 to adjust the tightness or tension of the rotational movement of deflection arm 75 by effectively compressing or releasing the rocker member 78 against the washer 119 (e.g., a Belleville type) and the control handle housing half 16 b.

The dial 101 has a generally circular cross section with a circumferential edge 115 having a friction-inducing surface (FIG. 17). A central circular protrusion 105 and a plurality of prongs 106 (FIG. 17) situated along a diameter of the dial project from a surface 104 of the dial 101.

The locking plate 102 is sandwiched between the dial 101 and the handle housing 16 b (FIG. 20). The locking plate 102 (FIG. 18) has a central larger hole 107 and two smaller holes 108, all three of which extend through the entire thickness of the locking plate. The two prongs 106 of the dial 101 are adapted to be inserted through the smaller holes 108 in the plate 102 (FIG. 21) and received in semi-circular grooves 109 (FIG. 19) formed in an outer surface of the housing half 16 b. The grooves 109 limit the degree of rotation of the dial 101 in clockwise and counterclockwise directions. The central hole 107 of the plate 102 (FIG. 18) has different cross-sections that include a larger circular cross-section 107 a and a smaller circular cross-section 107 b. The larger circular cross-section 107 a receives a head 112 of a cap screw 103, and the smaller circular cross-section 107 b receives a threaded body 115 of the cap screw 103 (FIG. 14a ).

The threaded body 115 of the cap screw 103 extending through the central hole 107 of the locking plate 102 engages the retaining nut 136 situated in the opening 143 of the rocker member 78. A head 115 of the nut abuts and is anchored against a neck 132 formed in the inner surface of the opening 143 of the rocker member 78. The opening 120 b in the housing half 16 b (FIG. 21) has a larger cross section 122 and a smaller cross section 124. The smaller cross section 124 has a polygonal shape which matches a polygonal (e.g., hexagonal) end 126 of the nut 136 so that the nut 136 is effectively locked against rotation relative to the housing handle 16 b.

The central protrusion 105 of the dial 101 (FIG. 17) forms a press or interference fit with the head 112 of the cap screw 103 to create rotational alignment between these two components. The prongs 106 of the dial 101 lock and rotationally couple the dial 101 and the lock plate 102, and the cap screw 103 is rotationally coupled to the locking plate 102. Coupling of the dial 101 and the locking plate 102 may also be achieved by means of welding the two components together. In that case, the prongs 106 need not protrude from the dial 101 but can instead extend from the locking plate 102.

Between the polygonal end 126 of the nut 136 and the housing handle 16 b is the washer 119 whose compression against the nut 136 and the housing handle 16 b is adjustable by the user's rotation of the dial 101 which tightens or releases the engagement between cap screw 103 and the nut 136, thus increasing or decreasing the ease with which the rocker member 78 and hence the deflection arm 75 can be rotated.

Components that extend through the control handle, including, for example, the lead wires 40 and the contraction wire 35 also enter the control handle at the distal end. In the illustrated embodiment of FIG. 9, these components extend along the longitudinal axis of the control handle. A protective tubing 152 through which the components extend can be provided, positioned between the two deflection puller members 42 and through a channel 150 form through the width dimension W of the rocker member 78 (FIG. 11). Distal and proximal portions of the channel 150 have indents, e.g., triangular or wedge-shaped, 151 (FIGS. 9 and 11) to allow the rocker member 78 to rotate freely within a predetermined range of angles, e.g., about ±45 degrees of the longitudinal axis of the control handle 16, without interference by the tubing 152 and the components therethrough.

Alternatively, the components extending through the control handle, with the exception of the contraction wire 35, are routed on an off-axis path 153 diverging from the deflection puller members 42 at entry into the distal end of the control handle 16. The components thus extend along the periphery of the housing handle, bypassing the rocker member 78.

It is understood that the distance between the distal end of the compression coils 44 and the distal anchor sites of each deflection puller members 42 in the intermediate section 14 determines the curvature of the intermediate section 14 in the direction of the deflection puller members. For example, an arrangement wherein the two deflection puller members 42 are anchored at different distances from the distal ends of the compression coils 44 allows a long reach curve in a first plane and a short reach curve in a plane 90 .degree. from the first, i.e., a first curve in one plane generally along the axis of the intermediate section 14 before it is deflected and a second curve distal to the first curve in a plane transverse, and preferably normal to the first plane. The high torque characteristic of the catheter intermediate section 14 reduces the tendency for the deflection in one direction to deform the deflection in the other direction. Suitable deflection control handles and parts thereof for use with such a catheter are described in U.S. patent application Ser. No. 08/924,611, filed Sep. 5, 1997, entitled “Omni-Directional Steerable Catheter”, Ser. No. 09/130,359, filed Aug. 7, 1998, entitled “Bi-Directional Control Handle for Steerable Catheter”, and Ser. No. 09/143,426, filed Aug. 28, 1998, entitled “Bidirectional Steerable Catheter with Bidirectional Control Handle”, the entire disclosures of which are hereby incorporated by reference.

For adjusting the mapping assembly 17 by means of a third puller member, e.g., the contraction wire 35, a distal end of the contraction wire extending between the two deflection puller members 42 within the control handle is anchored in the control handle for actuation by means of a rotational control assembly 200. In the illustrated embodiment of FIG. 23, the rotational control assembly 200 includes an outer rotational cam 202, a pulley shaft 204 and a pulley 206 around which the third puller member 35 is wrapped. The cam 202 closely surrounds the proximal portion 116 of the control handle and as the proximal portion 116 has a cylindrical shape, the rotational cam is in a circumferential relationship with the proximal portion so that it can rotate about a longitudinal central axis 205 of the proximal portion 116 on an outer surface 208 of the proximal portion and serve as a rotational interface between the user and internal components of the rotational control assembly 200. In that regard, the outer surface 208 is sufficiently smooth such that the cam 202 can rotate on it with minimal frictional forces. A friction-inducing surface can be provided on an outer surface of the cam 202 to facilitate manipulation and rotation by the user.

The proximal portion 116 under the cam 202 has two diametrically opposing guide slots 208 extending axially in a direction parallel to the longitudinal axis 205 of the proximal portion 116. The cam 202 has on its inner surface two opposing helical tracks or grooves 210 extending about the longitudinal axis 205. The helical grooves 210 are configured such that any plane perpendicular to the longitudinal axis intersects the grooves along a diameter of the proximal portion 116. The shaft 204 extends diametrically between the two guide slots 208, traversing the interior of the proximal portion at an angle generally perpendicular to the longitudinal axis 205. The guide slots 208 are sized so that the shaft 204 can pass through the slots and have each of its two opposing ends 212 be received in a respective helical groove on the inner surface of the cam. As such, the length of the shaft is greater than an outer diameter of the proximal portion 116 but lesser than an outer diameter of the cam 202. Accordingly, the helical grooves 210 are sized to receive the ends 212 and allow the ends to slide therein.

Mounted on the shaft, for example, at or near a midpoint of the length of the shaft, is the pulley 206 on which the third puller member is wrapped. The third puller member which can be any suitable material, including a puller wire or contraction wire, has a proximal end (not shown) that is anchored to the control handle or to any other rigidly mounted component within the control handle, at a location distal of the distal ends of the guide slots. Longitudinal movement of the contraction wire 35 relative to the catheter body 12 can effectuate, for example, contraction and expansion of the mapping assembly 17.

With reference to embodiment of FIGS. 1, 23 and 24, the rotational control assembly 200 is positioned proximal the deflection control assembly 74, although it is understood that it can be positioned distal the deflection control assembly 74. In the disclosed embodiment, the cam 202 is mounted on the proximal portion 116 of the control handle. The cam 202 can be formed from as a solid piece that slides onto the proximal portion and is snap-fitted over the two ends 212 of the shaft 204. Alternatively, the cam can be formed of two halves that are snap-fit to each other or joined by glue or sonic welding over the two ends of the shaft.

In operation, the rotational control assembly 200 is manipulated by means of the cam 202. As a user holds the control handle 16 and rotates the cam with his thumb and forefinger to contract or expand the mapping assembly, the two opposing helical tracks 210 on the inner surface are rotated relative to the proximal portion 116 thereby exerting a force on the shaft 204 via the ends 212 received in the tracks 210 to diametrically spin about the central longitudinal axis 205 of the control handle. However, because the shaft 204 extends through the guide slots 208 of the proximal portion 116, the guide slots limit the shaft to a translational movement proximally or distally along the longitudinal axis depending on the direction of rotation of the cam 202 as the ends 212 slide in the helical tracks 210. As the shaft 204 moves proximally or distally, the pulley 206 thereon correspondingly moves proximally or distally thereby drawing or releasing the third puller member 35. Advantageously, the rotational control assembly provides a multiplied linear motion of the third puller member, with greater sensitivity in the amount of motion controlled by the user. In the disclosed embodiment of FIG. 24, each helix 210 has a rotation of about 540° (360°+180°). However, it is understood that the rotation of each helix can range between about 180° to 720° depending on how much contraction/deflection and/or how much sensitivity is desired.

Lead wires and other components (e.g., thermocouple wires, cables, irrigation tubing) extending through proximal portion 116 in a protective tubing so as not to interfere with the interior components of the rotational control assembly.

In use, a suitable guiding sheath is inserted into the patient with its distal end positioned at a desired mapping location. An example of a suitable guiding sheath for use in connection with the present invention is the Preface™ Braiding Guiding Sheath, commercially available from Biosense Webster, Inc. (Diamond Bar, Calif.). The distal end of the sheath is guided into one of the chamber, for example, the atria. A catheter in accordance with the present invention is fed through the guiding sheath until its distal end extends out of the distal end of the guiding sheath. As the catheter is fed through the guiding sheath, the mapping assembly 17 is straightened to fit through the sheath. Once the distal end of the catheter is positioned at the desired mapping location, the guiding sheath is pulled proximally, allowing the deflectable intermediate section 14 and mapping assembly 17 to extend outside the sheath, and the mapping assembly 17 returns to its original shape due to the shape-memory of the support member 54.

By manipulating and rotating the deflection arm 75 of the deflection control assembly 74 to deflect the intermediate section 14, the mapping assembly 17 is then inserted into a pulmonary vein or other tubular region (such as the superior vena cava, or inferior vena cava) so that the outer circumference of the generally circular main region 39 of the assembly 17 is in contact with a circumference inside the tubular region. Turning the deflection arm 75 in one direction deflects the intermediate section 14 to that direction. Turning the deflection 75 in the opposite direction deflects the intermediate section 14 to that opposite direction. Tension of the deflection 75 is adjusted by manipulating and rotating the dial 101. Turning the dial 101 in one direction increases the tension. Turning the dial 101 in the opposition direction decreases the tension. Preferably at least about 50%, more preferably at least about 70%, and still more preferably at least about 80% of the circumference of the generally circular main region is in contact with a circumference inside the tubular region.

The circular arrangement of the electrodes 26 permits measurement of the electrical activity at that circumference of the tubular structure so that ectopic beats between the electrodes can be identified. The size of the generally circular main region 39 permits measurement of electrical activity along a diameter of a pulmonary vein or other tubular structure of or near the heart because the circular main region has a diameter generally corresponding to that of a pulmonary vein or the coronary sinus. By manipulating and rotating the cam 202 of the rotational assembly 200, the assembly 17, in particular, the generally circular main region 39, is contracted to fit the pulmonary vein or other tubular structure.

In accordance with a feature of the present invention, rotational motion of the cam results in linear motion of the shaft and the pulley along the central longitudinal axis of the control handle. The shaft rides along the helical grooves of the cam as it is rotated. The opposing linear guide slots of the proximal portion of the control handle ensure that the shaft maintains its general perpendicular orientation resulting in linear motion of the shaft relative to the proximal portion. As the shaft translates along the longitudinal axis, the pulley is also moved wherein its linear displacement results in twice the linear displacement of the third puller member. In the disclosed embodiment, the contraction wire is drawn proximally by the rotational control assembly to tighten and decrease the diameter of the generally circular region 39 when the cam is turned in one direction. By turning the cam in the opposition direction, the contraction wire 35 is released to release the generally circular region 39 such that it expands its diameter.

The preceding description has been presented with reference to presently preferred embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention. It is understood that the present invention is applicable to multiplying linear motion of a puller wire, contraction wire, or any other object requiring insertion, removal, or tensioning within a medical device, including the disclosed electrophysiology catheter. As understood by one of ordinary skill in the art, the drawings are not necessarily to scale. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fair scope. 

What is claimed is:
 1. A method of mapping tissue, the method comprising: introducing a distal end of a medical device to the tissue, the medical device comprising: an elongated body; a member distal the elongated body, the member having a configuration; a control handle proximal the elongated body, the control handle having a longitudinal axis; a control assembly comprising a rotational cam, a shaft, and a pulley, the rotational cam being in a circumferential relationship with a portion of the control handle and configured for rotation about the longitudinal axis, the rotational cam having an inner surface with two opposing helical tracks, the portion of the control handle having two opposing linear guide slots extending in parallel with the longitudinal axis, the shaft extending along a diameter of the portion of the control handle generally perpendicular to the longitudinal axis, the shaft having two opposing ends, each of which extends through a respective one of the two opposing linear guide slots and is received in a respective one of the two opposing helical tracks, the pulley being mounted on the shaft; and a puller member wrapped about the pulley, rotating the rotational cam about the longitudinal axis to thereby actuate movement of the shaft relative to the control handle along the longitudinal axis, thereby acting on the puller member via the pulley to change the configuration of the member; and mapping the tissue with the member.
 2. The method according to claim 1, wherein the rotation of the rotational cam results in contraction of the member.
 3. The method according to claim 1, wherein the rotation of the rotational cam results in expansion of the member.
 4. The method according to claim 1, wherein the rotation of the rotational cam results in deflection of the member.
 5. The method according to claim 1, wherein the rotation of the rotational cam actuates the shaft to rotate about a longitudinal axis of the shaft and translate along the longitudinal axis of the control handle while remaining generally perpendicular thereto.
 6. The method according to claim 1, wherein the rotational cam is outside of the portion of the control handle with which the rotational cam is in a circumferential relationship.
 7. The method according to claim 1, wherein the rotation of the rotational cam in one direction expands the member and the rotation of the rotational cam in an opposite direction contracts the member.
 8. The method according to claim 1, wherein the rotation of the rotational cam results in the two opposing ends of the shaft riding along their respective ones of the two opposing helical tracks.
 9. The method according to claim 1, wherein the shaft remains generally perpendicular to the longitudinal axis of the control handle as the rotational cam is rotated.
 10. The method according to claim 1, wherein the shaft moves within the two opposing linear guide slots as the rotational cam is rotated.
 11. A method of mapping tissue in a patient, the method comprising: introducing a distal end of a catheter to the tissue in the patient, the catheter comprising: a catheter body, a deflectable intermediate section distal the catheter body, a mapping assembly distal the intermediate section, the mapping assembly having a generally circular portion, a control handle proximal the catheter body, the control handle having a longitudinal axis and comprising: a deflection control assembly; and a rotational control assembly comprising a rotational cam, a shaft, and a pulley, the rotational cam being in a circumferential relationship with a portion of the control handle and configured for rotation about the longitudinal axis, the rotational cam having an inner surface with two opposing helical tracks, the portion of the control handle having two opposing guide slots extending in parallel with the longitudinal axis, the shaft extending along a diameter of the portion of the control handle generally perpendicular to the longitudinal axis, the shaft having two opposing ends, each of which extends through a respective one of the two opposing guide slots and is received in a respective one of the two opposing helical tracks, the pulley being mounted on the shaft, first and second puller members responsive to the deflection control assembly configured to deflect the intermediate section, and a third puller member responsive to the rotational control assembly configured to contract or expand the generally circular portion of the mapping assembly; either activating the rotational control assembly to thereby contract or expand the generally circular portion of the mapping assembly, or activating the deflection control assembly to thereby deflect the intermediate section; and mapping the tissue with the mapping assembly.
 12. The method according to claim 11, wherein a proximal end of the third puller member is anchored inside the control handle at a location distal of the shaft.
 13. The method according to claim 11, wherein the rotational cam is outside of the portion of the control handle with which the rotational cam is in a circumferential relationship.
 14. The method according to claim 11, wherein the rotation of the rotational cam results in contraction of the mapping assembly.
 15. The method according to claim 11, wherein the rotation of the rotational cam results in expansion of the mapping assembly.
 16. The method according to claim 11, wherein the rotation of the rotational cam actuates the shaft to rotate about a longitudinal axis of the shaft and translate along the longitudinal axis of the control handle while remaining generally perpendicular thereto.
 17. The method according to claim 11, wherein the rotation of the rotational cam in one direction expands the mapping assembly and the rotation of the rotational cam in an opposite direction contracts the mapping assembly.
 18. The method according to claim 11, wherein the two opposing ends of the shaft ride along their respective ones of the two opposing helical tracks as the rotational cam is rotated.
 19. The method according to claim 11, wherein the shaft remains generally perpendicular to the longitudinal axis of the control handle as the rotational cam is rotated.
 20. The method according to claim 11, wherein the shaft moves within the two opposing guide slots as the rotational cam is rotated. 